source/libcli/raw/smb_signing.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3    SMB Signing Code
   4    Copyright (C) Jeremy Allison 2002.
   5    Copyright (C) Andrew Bartlett <abartlet@samba.org> 2002-2003
   6    Copyright (C) James J Myers <myersjj@samba.org> 2003
   7
   8    This program is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 2 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program; if not, write to the Free Software
  20    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  21 */
  22
  23 #include "includes.h"
  24 #include "libcli/raw/libcliraw.h"
  25 #include "lib/crypto/crypto.h"
  26
  27 /***********************************************************
  28  SMB signing - Common code before we set a new signing implementation
  29 ************************************************************/
  30 BOOL set_smb_signing_common(struct smb_signing_context *sign_info)
  31 {
  32         if (sign_info->doing_signing) {
  33                 DEBUG(5, ("SMB Signing already in progress, so we don't start it again\n"));
  34                 return False;
  35         }
  36
  37         if (!sign_info->allow_smb_signing) {
  38                 DEBUG(5, ("SMB Signing has been locally disabled\n"));
  39                 return False;
  40         }
  41
  42         return True;
  43 }
  44
  45 /***********************************************************
  46  SMB signing - Common code before we set a new signing implementation
  47 ************************************************************/
  48 static BOOL smbcli_set_smb_signing_common(struct smbcli_transport *transport)
  49 {
  50         if (!set_smb_signing_common(&transport->negotiate.sign_info)) {
  51                 return False;
  52         }
  53
  54         if (!(transport->negotiate.sec_mode &
  55               (NEGOTIATE_SECURITY_SIGNATURES_REQUIRED|NEGOTIATE_SECURITY_SIGNATURES_ENABLED))) {
  56                 DEBUG(5, ("SMB Signing is not negotiated by the peer\n"));
  57                 return False;
  58         }
  59
  60         /* These calls are INCOMPATIBLE with SMB signing */
  61         transport->negotiate.readbraw_supported = False;
  62         transport->negotiate.writebraw_supported = False;
  63
  64         return True;
  65 }
  66
  67 void mark_packet_signed(struct request_buffer *out)
  68 {
  69         uint16_t flags2;
  70         flags2 = SVAL(out->hdr, HDR_FLG2);
  71         flags2 |= FLAGS2_SMB_SECURITY_SIGNATURES;
  72         SSVAL(out->hdr, HDR_FLG2, flags2);
  73 }
  74
  75 BOOL signing_good(struct smb_signing_context *sign_info,
  76                          unsigned int seq, BOOL good)
  77 {
  78         if (good) {
  79                 if (!sign_info->doing_signing) {
  80                         DEBUG(5, ("Seen valid packet, so turning signing on\n"));
  81                         sign_info->doing_signing = True;
  82                 }
  83                 if (!sign_info->seen_valid) {
  84                         DEBUG(5, ("Seen valid packet, so marking signing as 'seen valid'\n"));
  85                         sign_info->seen_valid = True;
  86                 }
  87         } else {
  88                 if (!sign_info->seen_valid) {
  89                         /* If we have never seen a good packet, just turn it off */
  90                         DEBUG(5, ("signing_good: signing negotiated but not required and peer\n"
  91                                   "isn't sending correct signatures. Turning off.\n"));
  92                         smbcli_set_signing_off(sign_info);
  93                         return True;
  94                 } else {
  95                         /* bad packet after signing started - fail and disconnect. */
  96                         DEBUG(0, ("signing_good: BAD SIG: seq %u\n", seq));
  97                         return False;
  98                 }
  99         }
 100         return True;
 101 }
 102
 103 void sign_outgoing_message(struct request_buffer *out, DATA_BLOB *mac_key, uint_t seq_num)
 104 {
 105         uint8_t calc_md5_mac[16];
 106         struct MD5Context md5_ctx;
 107
 108         /*
 109          * Firstly put the sequence number into the first 4 bytes.
 110          * and zero out the next 4 bytes.
 111          */
 112         SIVAL(out->hdr, HDR_SS_FIELD, seq_num);
 113         SIVAL(out->hdr, HDR_SS_FIELD + 4, 0);
 114
 115         /* mark the packet as signed - BEFORE we sign it...*/
 116         mark_packet_signed(out);
 117
 118         /* Calculate the 16 byte MAC and place first 8 bytes into the field. */
 119         MD5Init(&md5_ctx);
 120         MD5Update(&md5_ctx, mac_key->data, mac_key->length);
 121         MD5Update(&md5_ctx,
 122                   out->buffer + NBT_HDR_SIZE,
 123                   out->size - NBT_HDR_SIZE);
 124         MD5Final(calc_md5_mac, &md5_ctx);
 125
 126         memcpy(&out->hdr[HDR_SS_FIELD], calc_md5_mac, 8);
 127
 128         DEBUG(5, ("sign_outgoing_message: SENT SIG (seq: %d): sent SMB signature of\n",
 129                   seq_num));
 130         dump_data(5, calc_md5_mac, 8);
 131 /*      req->out.hdr[HDR_SS_FIELD+2]=0;
 132         Uncomment this to test if the remote server actually verifies signitures...*/
 133 }
 134
 135 BOOL check_signed_incoming_message(struct request_buffer *in, DATA_BLOB *mac_key, uint_t seq_num)
 136 {
 137         BOOL good;
 138         uint8_t calc_md5_mac[16];
 139         uint8_t *server_sent_mac;
 140         uint8_t sequence_buf[8];
 141         struct MD5Context md5_ctx;
 142         const size_t offset_end_of_sig = (HDR_SS_FIELD + 8);
 143         int i;
 144         const int sign_range = 0;
 145
 146         /* room enough for the signature? */
 147         if (in->size < NBT_HDR_SIZE + HDR_SS_FIELD + 8) {
 148                 return False;
 149         }
 150
 151         if (!mac_key->length) {
 152                 /* NO key yet */
 153                 return False;
 154         }
 155
 156         /* its quite bogus to be guessing sequence numbers, but very useful
 157            when debugging signing implementations */
 158         for (i = 0-sign_range; i <= 0+sign_range; i++) {
 159                 /*
 160                  * Firstly put the sequence number into the first 4 bytes.
 161                  * and zero out the next 4 bytes.
 162                  */
 163                 SIVAL(sequence_buf, 0, seq_num + i);
 164                 SIVAL(sequence_buf, 4, 0);
 165
 166                 /* get a copy of the server-sent mac */
 167                 server_sent_mac = &in->hdr[HDR_SS_FIELD];
 168
 169                 /* Calculate the 16 byte MAC and place first 8 bytes into the field. */
 170                 MD5Init(&md5_ctx);
 171                 MD5Update(&md5_ctx, mac_key->data,
 172                           mac_key->length);
 173                 MD5Update(&md5_ctx, in->hdr, HDR_SS_FIELD);
 174                 MD5Update(&md5_ctx, sequence_buf, sizeof(sequence_buf));
 175
 176                 MD5Update(&md5_ctx, in->hdr + offset_end_of_sig,
 177                           in->size - NBT_HDR_SIZE - (offset_end_of_sig));
 178                 MD5Final(calc_md5_mac, &md5_ctx);
 179
 180                 good = (memcmp(server_sent_mac, calc_md5_mac, 8) == 0);
 181
 182                 if (i == 0) {
 183                         if (!good) {
 184                                 DEBUG(5, ("check_signed_incoming_message: BAD SIG (seq: %d): wanted SMB signature of\n", seq_num + i));
 185                                 dump_data(5, calc_md5_mac, 8);
 186
 187                                 DEBUG(5, ("check_signed_incoming_message: BAD SIG (seq: %d): got SMB signature of\n", seq_num + i));
 188                                 dump_data(5, server_sent_mac, 8);
 189                         } else {
 190                                 DEBUG(15, ("check_signed_incoming_message: GOOD SIG (seq: %d): got SMB signature of\n", seq_num + i));
 191                                 dump_data(5, server_sent_mac, 8);
 192                         }
 193                 }
 194
 195                 if (good) break;
 196         }
 197
 198         if (good && i != 0) {
 199                 DEBUG(0,("SIGNING OFFSET %d (should be %d)\n", i, seq_num));
 200         }
 201
 202         return good;
 203 }
 204
 205 static void smbcli_req_allocate_seq_num(struct smbcli_request *req)
 206 {
 207         req->seq_num = req->transport->negotiate.sign_info.next_seq_num;
 208
 209         /* some requests (eg. NTcancel) are one way, and the sequence number
 210            should be increased by 1 not 2 */
 211         if (req->sign_single_increment) {
 212                 req->transport->negotiate.sign_info.next_seq_num += 1;
 213         } else {
 214                 req->transport->negotiate.sign_info.next_seq_num += 2;
 215         }
 216 }
 217
 218 /***********************************************************
 219  SMB signing - Simple implementation - calculate a MAC to send.
 220 ************************************************************/
 221 void smbcli_request_calculate_sign_mac(struct smbcli_request *req)
 222 {
 223 #if 0
 224         /* enable this when packet signing is preventing you working out why valgrind
 225            says that data is uninitialised */
 226         file_save("pkt.dat", req->out.buffer, req->out.size);
 227 #endif
 228
 229         switch (req->transport->negotiate.sign_info.signing_state) {
 230         case SMB_SIGNING_ENGINE_OFF:
 231                 break;
 232
 233         case SMB_SIGNING_ENGINE_BSRSPYL:
 234                 /* mark the packet as signed - BEFORE we sign it...*/
 235                 mark_packet_signed(&req->out);
 236
 237                 /* I wonder what BSRSPYL stands for - but this is what MS
 238                    actually sends! */
 239                 memcpy((req->out.hdr + HDR_SS_FIELD), "BSRSPYL ", 8);
 240                 break;
 241
 242         case SMB_SIGNING_ENGINE_ON:
 243
 244                 smbcli_req_allocate_seq_num(req);
 245                 sign_outgoing_message(&req->out,
 246                                       &req->transport->negotiate.sign_info.mac_key,
 247                                       req->seq_num);
 248                 break;
 249         }
 250         return;
 251 }
 252
 253
 254 /**
 255  SMB signing - NULL implementation
 256
 257  @note Used as an initialisation only - it will not correctly
 258        shut down a real signing mechanism
 259 */
 260 BOOL smbcli_set_signing_off(struct smb_signing_context *sign_info)
 261 {
 262         DEBUG(5, ("Shutdown SMB signing\n"));
 263         sign_info->doing_signing = False;
 264         sign_info->next_seq_num = 0;
 265         data_blob_free(&sign_info->mac_key);
 266         sign_info->signing_state = SMB_SIGNING_ENGINE_OFF;
 267         return True;
 268 }
 269
 270 /**
 271  SMB signing - TEMP implementation - setup the MAC key.
 272
 273 */
 274 BOOL smbcli_temp_set_signing(struct smbcli_transport *transport)
 275 {
 276         if (!smbcli_set_smb_signing_common(transport)) {
 277                 return False;
 278         }
 279         DEBUG(5, ("BSRSPYL SMB signing enabled\n"));
 280         smbcli_set_signing_off(&transport->negotiate.sign_info);
 281
 282         transport->negotiate.sign_info.mac_key = data_blob(NULL, 0);
 283         transport->negotiate.sign_info.signing_state = SMB_SIGNING_ENGINE_BSRSPYL;
 284
 285         return True;
 286 }
 287
 288 /***********************************************************
 289  SMB signing - Simple implementation - check a MAC sent by server.
 290 ************************************************************/
 291 /**
 292  * Check a packet supplied by the server.
 293  * @return False if we had an established signing connection
 294  *         which had a back checksum, True otherwise
 295  */
 296 BOOL smbcli_request_check_sign_mac(struct smbcli_request *req)
 297 {
 298         BOOL good;
 299
 300         switch (req->transport->negotiate.sign_info.signing_state)
 301         {
 302         case SMB_SIGNING_ENGINE_OFF:
 303                 return True;
 304         case SMB_SIGNING_ENGINE_BSRSPYL:
 305         case SMB_SIGNING_ENGINE_ON:
 306         {
 307                 if (req->in.size < (HDR_SS_FIELD + 8)) {
 308                         return False;
 309                 } else {
 310                         good = check_signed_incoming_message(&req->in,
 311                                                              &req->transport->negotiate.sign_info.mac_key,
 312                                                              req->seq_num+1);
 313
 314                         return signing_good(&req->transport->negotiate.sign_info,
 315                                             req->seq_num+1, good);
 316                 }
 317         }
 318         }
 319         return False;
 320 }
 321
 322
 323 /***********************************************************
 324  SMB signing - Simple implementation - setup the MAC key.
 325 ************************************************************/
 326 BOOL smbcli_simple_set_signing(TALLOC_CTX *mem_ctx,
 327                                struct smb_signing_context *sign_info,
 328                                const DATA_BLOB *user_session_key,
 329                                const DATA_BLOB *response)
 330 {
 331         if (sign_info->mandatory_signing) {
 332                 DEBUG(5, ("Mandatory SMB signing enabled!\n"));
 333         }
 334
 335         DEBUG(5, ("SMB signing enabled!\n"));
 336
 337         if (response && response->length) {
 338                 sign_info->mac_key = data_blob_talloc(mem_ctx, NULL, response->length + user_session_key->length);
 339         } else {
 340                 sign_info->mac_key = data_blob_talloc(mem_ctx, NULL, user_session_key->length);
 341         }
 342
 343         memcpy(&sign_info->mac_key.data[0], user_session_key->data, user_session_key->length);
 344
 345         if (response && response->length) {
 346                 memcpy(&sign_info->mac_key.data[user_session_key->length],response->data, response->length);
 347         }
 348
 349         dump_data_pw("Started Signing with key:\n", sign_info->mac_key.data, sign_info->mac_key.length);
 350
 351         /* Initialise the sequence number */
 352         sign_info->next_seq_num = 0;
 353
 354         sign_info->signing_state = SMB_SIGNING_ENGINE_ON;
 355
 356         return True;
 357 }
 358
 359
 360 /***********************************************************
 361  SMB signing - Simple implementation - setup the MAC key.
 362 ************************************************************/
 363 BOOL smbcli_transport_simple_set_signing(struct smbcli_transport *transport,
 364                                          const DATA_BLOB user_session_key,
 365                                          const DATA_BLOB response)
 366 {
 367         if (!smbcli_set_smb_signing_common(transport)) {
 368                 return False;
 369         }
 370
 371         return smbcli_simple_set_signing(transport,
 372                                          &transport->negotiate.sign_info,
 373                                          &user_session_key,
 374                                          &response);
 375 }
 376
 377
 378 BOOL smbcli_init_signing(struct smbcli_transport *transport)
 379 {
 380         transport->negotiate.sign_info.mac_key = data_blob(NULL, 0);
 381         if (!smbcli_set_signing_off(&transport->negotiate.sign_info)) {
 382                 return False;
 383         }
 384
 385         switch (lp_client_signing()) {
 386         case SMB_SIGNING_OFF:
 387                 transport->negotiate.sign_info.allow_smb_signing = False;
 388                 break;
 389         case SMB_SIGNING_SUPPORTED:
 390         case SMB_SIGNING_AUTO:
 391                 transport->negotiate.sign_info.allow_smb_signing = True;
 392                 break;
 393         case SMB_SIGNING_REQUIRED:
 394                 transport->negotiate.sign_info.allow_smb_signing = True;
 395                 transport->negotiate.sign_info.mandatory_signing = True;
 396                 break;
 397         }
 398         return True;
 399 }